Data traffic in mobile telecommunications networks is continually increasing. Consequently, operators are deploying heterogeneous access networks that make use of multiple radio access technologies (RATs) in order to provide greater capacity, particularly in high traffic areas and areas that otherwise have poor network coverage.
Typically, the radio access technologies utilised as part of these heterogeneous access networks include UMTS Radio Access Network (UTRAN) and an Evolved UTRAN (eUTRAN), and Wi-Fi/WLAN RAN. For example, FIG. 1 illustrates schematically a heterogeneous access network comprised of a UTRAN, an eUTRAN, and a Wi-Fi/WLAN RAN. In this regard, both the UTRAN and eUTRAN standards are defined by the 3rd Generation Partnership Project (3GPP), and the relevant 3GPP standards therefore define capabilities for interaction between these 3GPP networks. In contrast, the Wi-Fi/WLAN standards are defined by the Institute of Electrical and Electronics Engineers (IEEE), and neither the IEEE standards nor the 3GPP standards define capabilities for interaction between a Wi-Fi/WLAN network and a 3GPP network. Furthermore, as a WLAN network and a 3GPP network are part of separate domains that use different management systems, different paradigms, different identities etc., there is no mechanism that allows either network to determine information relating to the other network.
Consequently, for a device/user terminal (i.e. user equipment (UE), station (STA) etc) that is both 3GPP and WiFi/WLAN capable, and can therefore move between a 3GPP network and a WLAN, the decision to move between a 3GPP network and a WLAN will be made by the user terminal. For example, for most currently available user terminals, when the user terminal is within the coverage of both a WLAN and a 3GPP network, the user terminal will automatically attempt to connect to the WLAN and will detach from the 3GPP network. As a further example, a user terminal could decide to attempt to associate with a WLAN if the connection to a 3GPP network is poor. In such circumstances, neither the 3GPP network nor the WLAN will have any knowledge of each other, and it will therefore appear to the serving/source network (i.e. the network from which the user terminal is moving) as if the user terminal is merely disconnecting, whilst the user terminal has in fact moved to an alternative network.
It has been recognised here that an issue that arises from the fact that the decision to move/switch between a WLAN and a 3GPP network is made by the user terminal, is that at the very least the decision is made by the user terminal without knowledge of the conditions within or performance of the destination/target network, and possibly without taking into account the performance that the user terminal is receiving from the serving/source network. For example, if a user terminal connected to a 3GPP network were to automatically connect to a WLAN upon detection, and therefore disconnect from the 3GPP network, this could result in an overload in the WLAN and/or underutilisation of the 3GPP network. By way of further example, if a user terminal associated with a WLAN were to determine that the performance received from the WLAN is poor, and therefore proceeded to connect to a 3GPP network and disassociate from the WLAN, it could be the case that the 3GPP network is heavily loaded, such that moving from the WLAN to the 3GPP network has a detrimental effect on the performance received by the user terminal.